The present invention relates to power distribution systems. More specifically, the present invention relates to synchronous frame regulation in a power distribution system.
It is not unusual for a power distribution system to have a three-phase distribution feeder that supplies multiple loads. However, different loads connected to the feeder can cause the line voltage to become unbalanced. The voltage is considered unbalanced if the line-to-line voltages are not equal. For instance, consider a situation when a three-phase motor and a single-phase load are connected to a distribution feeder line. If the three-phase motor and the single-phase load are operated at the same time, a voltage unbalance on the feeder line will occur.
When an unbalanced voltage is applied to an active rectifier, control algorithms used to regulate the active rectifier can cause third harmonic current to be generated in the power distribution system. These currents are extremely undesirable, partly because they affect the active rectifier's control and partly because they can cause overheating of the loads that receive power from the distribution system.